1. Field of the Invention
This present invention relates to a reading light for a vehicle interior. In particular, a reading light having a light source arranged in a light fixture housing, which includes a lens disposed in front of the light emitting direction of the light source.
2. Related Art
German Patent Application 25 07 857 A1 describes a reading light or a seat light for use with vehicles. The reading light includes a light fixture housing that includes a spherical light fixture body pivotally mounted in a receptacle in the light fixture housing. The light fixture body has an incandescent lamp or bulb light source that is surrounded by a reflector. A lens covers an opening in the light fixture housing and is positioned such that it receives light directly emitted from the light source.
A disadvantage of known reading light designs is that they are not suitable for light sources having a small beam width or spread factor; for example, light-emitting diodes. Another disadvantage of known reading light designs is that they are not suitable for producing a beam of light having a small beam width because the structural depth of the prior related art reading light devices is too great.
An object of the present invention is to provide a reading light structure capable of using light-emitting diodes as a light source and which produces a small or narrow beam of light.
This object and other objects of the present invention are achieved by providing a reading light, including a light source arranged in a light fixture housing, a second lens placed in front of the light source in the direction of light emission, and a first lens positioned between the light source and the second lens.
Due to the use of a lens system including a first lens and a second lens, even light sources having a relatively small beam width may be used. Moreover, the lens system may be constructed with a relatively small structural depth. In addition, the lens system according to the present invention provides a homogeneous plane of illumination. When using light-emitting diodes having arrays of individual so-called dies, the dies are not imaged sharply in the illumination plane which, would lead to a non-homogeneous light distribution in the illumination plane.
According to a preferred embodiment of the present invention, the light source is a light-emitting diode arranged at the focal point of the first lens, which is designed as a convergent lens. The first lens is in turn arranged at the focal point of the second lens. The first lens and a holder thereof form the orifice or aperture lens, and the second lens and a holder thereof form the field lens. This arrangement leads to a uniform light distribution or light intensity over an illuminated area.
According to another preferred embodiment of the present invention, the light source or the light-emitting diode is arranged between the focal point of the first lens and the first lens.
Therefore, because the focal point of the first lens is arranged behind the light-emitting diode or the stop plane, a compact reading light having a very small structural depth may be realized. The arrangement of the focal point behind the plane of the orifice also leads to a virtual object plane, with the result that the beam aperture or light panel may be increased in size, which in turn leads to an increase in efficiency of the light system. The light distribution of the illuminated area may therefore have its maximum at the center and decreases toward an edge thereof.
According to another preferred embodiment of the present invention, the second lens is designed as a Fresnel lens. Due to the use of a Fresnel lens, a uniform light intensity of the illuminated area can be achieved. It is also possible to design the second lens as a biconvex lens.
Due to the use of light-emitting diodes as the light source, a long lifetime of the light source with a low electric power can be achieved. Furthermore, when using light-emitting diodes, a small light outlet area can be implemented.
According to another preferred embodiment of the present invention, the light-emitting diode has a light fixture housing with two pins or two terminals as electric contacts, which may receive a plug that supplies electrical connectivity.
Accordingly, since the pins or terminals are used for receiving electricity, supplying electrical power by means of a plug is greatly simplified.
According to another preferred embodiment of the present invention, the plug for contacting the light-emitting diode also seals the light fixture housing on its rear side.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.